Infrared remote control and sensing technology infrared fiber optics for communication and are two important technological areas in modern electronics. In these applications, a sensitive and fast infrared (IR) detector is the most important element in the system.
Methods for making quantum well IR detectors are well known. In U.S. Pat. No. 4,873,555 entitled "Intraband Quantum Well Photodetector and Associated Method", issued Oct. 10, 1989, in the name of Coon et al., the applicant teaches a basic method for making a single-well detector and introduces the use of intraband or intersubband transitions for IR detection. Subsequently, a multiple quantum well (MQW) detector was disclosed by Bethea et al. in U.S. Pat. No. 4,894,526 entitled "Infrared Radiation Detector Device", issued Jan. 16, 1990. These detectors however, were limited having a fixed spectral response curve. Kwong-Kit Choi, in U.S. Pat. No. 5,013,918 entitled " Multicolour Infrared Photodetector discloses a multicolour detector based on coupled quantum wells; Choi's detector is comprised of units of thick and thin wells separated by a thin barrier. A thick quantum well having two confined states E.sub.1 and E.sub.2 and thin quantum well having one confined state E.sub.1 are brought close enough together so that the wells become coupled and the level structure becomes common to both wells. However, a physical limit of the thickness of the thin barrier constrains the range of the spectrum tuning range that Choi's device can detect.